In general, to multiple recording or reconstructing a two-dimensional digital signal onto a holography recording medium, the incident angle of a reference light beam with respect to the holography recording medium or the wavelength of a reference light beam is changed.
Typically, a galvanometer mirror has been used to control an incident angle of such a light beam (a reference light beam) (refer to, for example, Patent Document 1).
In addition, a planer galvanomirror that uses, for example, a gimbal torsion bar has been available (refer to, for example, Patent Document 2).
In Patent Document 2, a gimbal mechanism includes an outer movable plate that rotates about a first torsion bar and an inner movable plate that rotates about the second torsion bar that is disposed in a direction perpendicular to the first torsion bar. A reflecting mirror is mounted on the inner movable plate.
A flow of an electrical current in a planar coil of the outer movable plate allows the outer movable plate to rotate about the first torsion bar as a fulcrum (an axis). In addition, a flow of an electrical current in a planar coil of the inner movable plate allows the inner movable plate to rotate about the second torsion bar as a fulcrum (an axis). Such a galvanomirror is a two-axis actuator that can control the position of the total reflecting mirror in two axis directions.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-169122 (FIGS. 1 to 6)
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 7-175005 (FIG. 2)